Overflight, 104
If at any point during your journey through this book you paused for a moment over a term you wanted to clarify or investigate further and typed it into a search engine — and if that term happened to be in some way suspicious, a term like XKEYSCORE, for example — then congrats: you’re in the system, a victim of your own curiosity.
…
Imagine yourself sitting at a computer, about to visit a website. You open a Web browser, type in a URL, and hit Enter. The URL is, in effect, a request, and this request goes out in search of its destination server. Somewhere in the midst of its travels, however, before your request gets to that server, it will have to pass through TURBULENCE, one of the NSA’s most powerful weapons.
Specifically, your request passes through a few black servers stacked on top of one another, together about the size of a four−shelf bookcase. These are installed in special rooms at major private telecommunications buildings throughout allied countries, as well as in US embassies and on US military bases, and contain two critical tools. The first, TURMOIL, handles "passive collection," making a copy of the data coming through. The second, TURBINE, is in charge of "active collection" — that is, actively tampering with the users.
You can think of TURMOIL as a guard positioned at an invisible firewall through which Internet traffic must pass. Seeing your request, it checks its metadata for selectors, or criteria, that mark it as deserving of more scrutiny. Those selectors can be whatever the NSA chooses, whatever the NSA finds suspicious: a particular email address, credit card, or phone number; the geographic origin or destination of your Internet activity; or just certain keywords such as "anonymous Internet proxy" or "protest."